1. Field of the Invention
This invention relates to a lens used to condense or collimate substantially monochromatic light emitted from a laser or an LED, and in particular to a non-spherical single lens whose NA is up to the order of 0.35 and in which correction of aberrations is effected over a relatively wide field of view.
2. Related Background Art
Non-spherical single lenses have heretofore been proposed in Japanese Laid-open patent application Nos. 64714/1982, 201210/1982, 1983 (U.S. counterpart is U.S. Pat. No. 4,415,238) and Japanese Laid-open patent application No. 68711/1983. However, any of these propositions is designed chiefly as an objective for an optical head. Accordingly, in these lenses, correction of aberrations is effected only in a very slight range on and near the axis, and where these are used, for example, as collimators, aberrations are created unless a light source is disposed at a very much limited position the focus position on the optic axis of the lens, and thus, great pains have often been bestowed on assembly, adjustment, etc.